Imaging probes and catheters for volumetric intraluminal ultrasound imaging and related systems

ABSTRACT

A real time three dimensional ultrasound imaging probe apparatus is configured to be placed inside a body. The apparatus comprises an elongated body having proximal and distal ends with an ultrasonic transducer phased array connected to and positioned on the distal end of the elongated body. The ultrasonic transducer phased array is positioned to emit and receive ultrasonic energy for volumetric forward scanning from the distal end of the elongated body. The ultrasonic transducer phased array includes a plurality of sites occupied by ultrasonic transducer elements. At least one ultrasonic transducer element is absent from at least one of the sites, thereby defining an interstitial site. A tool is positioned at the interstitial site. In particular, the tool can be a fiber optic lead, a suction tool, a guide wire, an electrophysiological electrode, or an ablation electrode. Related systems are also discussed.

This invention was made with Government support under grant numberCA56475 from the National Institute of Health. The Government hascertain rights to this invention.

FIELD OF THE INVENTION

The present invention relates to the field of imaging in general and toultrasound imaging in particular.

BACKGROUND OF THE INVENTION

Ultrasonic imaging has been applied in many two dimensional systemsusing pulse echo B-mode tomography or B-scans. These systems displayechoes returning to an ultrasonic transducer as brightness levelsproportional to echo amplitude. The brightness levels may be used tocreate cross-sectional images of the object in the plane perpendicularto the transducer aperture.

Examination of objects in three dimensions has evolved using a number ofmodalities including x-ray, ultrasound, and nuclear magnetic resonance.In particular, improvements have been made in spatial resolution,dynamic range, display methods and data analysis. For example,ultrasound scanning of three-dimensional objects by sequential B-scansfollowed by off-line reconstruction and display of rendered images hasprogressed in recent years with the introduction of commercialthree-dimensional systems. Off-line rendering, however, may take severalminutes to produce a single three-dimensional scan.

In the area of high-speed three-dimensional ultrasound imaging, U.S.Pat. No. 4,596,145 to Smith and von Ramm discloses an acoustic imagingsystem capable of producing high-speed projection orthoscopic images, aswell as a single high-speed C-scan image using a two-dimensional arraytransducer and receive mode parallel processing. The C-scan image may bedefined as a planar section of the object parallel to the effectivetransducer aperture. In 1987, U.S. Pat. No. 4,694,434 to von Ramm andSmith disclosed a steered array acoustic imaging scanner capable ofproducing a high-speed pyramidal scan to obtain a volumetric(three-dimensional) image using a two-dimensional array transducer andreceive mode parallel processing.

High frequency intraluminal ultrasound imaging probes have beendeveloped, including circular arrays and mechanically steeredtransducers. The circular arrays and mechanically steered transducersproduce B-mode circular side scan geometries in which the ultrasoundbeam is swept through a 360° arc. The 360° arc may create a high-speedcircular image within a vessel or lumen with a maximum range ofapproximately one centimeter. For example, U.S. Pat. No. 3,938,502 toBom and U.S. Pat. No. 4,917,097 to Proudian, et al. disclose circulararrays of transducer elements within a catheter to produce a circularside scanning intraluminal B-mode image. U.S. Pat. No. 4,794,931 to Yockand U.S. Pat. No. 5,243,988 to Sieben, et al. disclose motor-drivenpiston transducers at the end of the catheters to produce circular sidescanning intervascular imaging.

Catheters may be used in conjunction with the systems described above toprovide intraluminal imaging. Intraluminal imaging may involve insertinga catheter, that includes an ultrasonic transducer phased array, intocoronary vessels, pulmonary arteries, the aorta, or venous structures.For example, U.S. Pat. No. 5,704,361 to Seward, et al. discloses avolumetric imaging ultrasound transducer under-fluid catheter system.The advantages of Seward may, however, be limited by the quality of theimaging provided therein. In particular, the catheter probes disclosedin Seward show the therapeutic tools adjacent to the transducer array onthe catheter tip, thereby reducing the area available for the transducerarray. Such an array may provide images having reduced spatialresolution. Moreover, the applications described in Seward may belimited to procedures involving catheters.

The catheters described above may be combined with electrodes or toolsto locate (cardiac electrophysiological mapping) and perform therapy on(radiofrequency ablation) or monitor tissue. For example, athree-dimensional ultrasound imaging device using a catheter may becombined with an ablation electrode to provide therapy to particulartissue. The therapy provided by the electrode, however, may be limitedby the registration between the image provided by the catheter and theelectrodes associated with the catheter. For example, a user may havedifficulty translating the image produced by the catheter to theposition of the electrode, thereby possibly creating difficulty inapplying the electrode to the intended tissue. Moreover, the electrodemay obscure the three dimensional ultrasound image when the electrode iswithin the field of view of the image.

In view of the above discussion, there exists a need to improve thequality of real-time three-dimensional imaging in intraluminalultrasound applications.

SUMMARY OF THE INVENTION

In view of the above discussion, it is an object of the presentinvention to provide improved ultrasonic imaging probes.

It is another object of the present invention to provide improvedtherapy in conjunction with ultrasonic imaging.

These and other objects are provided by a real time three dimensionalultrasound imaging probe configured to be placed inside a body. Theimaging probe includes an elongated body having proximal and distalends. An ultrasonic transducer phased array is connected to andpositioned on the distal end of the elongated body. The ultrasonictransducer phased array is configured to emit ultrasonic energy forvolumetric scanning from the distal end of the elongated body andreceive reflected ultrasonic energy. The ultrasonic transducer phasedarray includes a plurality of sites occupied by ultrasonic transducerelements. At least one ultrasonic transducer element is absent from atleast one of the sites, thereby defining an interstitial site. A tool ispositioned at the interstitial site. In particular, the tool can be afiber optic lead, a suction tool, a scalpel, a guide wire, anelectrophysiological electrode, or an ablation electrode. Positioningthe tool at an interstitial site allows a large ultrasonic transducerphased array aperture, thereby producing superior image resolution andsensitivity as compared to the prior art. Conventional probes mayinclude tools, positioned outside the ultrasonic transducer phasedarray, that reduce the aperture size of the ultrasonic transducer phasedarray. A reduced aperture size provides lower image resolution andsensitivity. Positioning the tool within the ultrasonic transducerphased array allows the user to accurately align the tool with thetissue to be treated more accurately, thereby making the probe easier touse and more effective.

In one aspect, a plurality of ultrasonic transducer elements are absentfrom a plurality of sites, defining a plurality of interstitial sites.The plurality of interstitial sites have a circular arrangement withinthe ultrasonic transducer phased array. The circular arrangement allowsa larger aperture size while limiting side lobe effects on the imaging.

In another aspect, the ultrasonic transducer elements are arranged in arow of ultrasonic transducer elements and a column of ultrasonictransducer elements, defining four quadrants of interstitial siteswithin the ultrasonic transducer phased array. The row of ultrasonictransducer elements is substantially perpendicular to the column ofultrasonic transducer elements. A tool can be positioned at aninterstitial site within each quadrant of the ultrasonic transducerphased array.

In still another aspect, a real time three dimensional ultrasoundimaging probe apparatus is configured to be placed inside a body. Theapparatus includes an elongated body having proximal and distal endswith an ultrasonic transducer phased array connected to and positionedon the distal end of the elongated body. The ultrasonic transducerphased array is configured to emit either forward or side scanningultrasonic energy for volumetric scanning from the distal end of theelongated body and receive reflected ultrasonic energy. An electrodeassembly is connected to and overlies the ultrasonic transducer phasedarray, wherein the electrode assembly is transparent to ultrasonicenergy.

The ultrasonically transparent electrode assembly allows the user tomore accurately apply the electrode to tissue within a region ofinterest, thereby allowing a reduction in the complexity associated withthe prior art. For example, the present invention allows the user toapply the electrode to the tissue by locating the tissue within theregion of interest using the real time three dimensional images. Incontrast, users of some conventional imaging probes locate the tissueand then manipulate an electrode to the tissue by understanding theregistration between the image and the physical location of theelectrode on the probe.

The present invention also provides increased image resolution andsensitivity (signal to noise ratio) by increasing the aperture size ofthe ultrasonic transducer phased array to include a majority of thesurface area of the distal end of elongated body. In particular,conventional ultrasonic transducer phased arrays cover a minority of thedistal end of the elongated body described therein. Moreover, the priorart generally discloses an ultrasonic transducer phased array inconjunction with conventional tools and electrodes positioned in closeproximity to the ultrasonic transducer phased array, thereby limitingthe size of the ultrasonic transducer phased array. As a result, imagesproduced by conventional imaging probes have less spatial resolution andsensitivity relative to those produced by the present invention.

The present invention also provides improved imaging over the prior artas applied to biopsy procedures. In particular, a real time threedimensional imaging biopsy apparatus configured to be inserted into abody includes an elongated body, having proximal and distal ends, thatis configured to be extended through a biopsy needle into the body. Anultrasonic transducer phased array is connected to and positioned on thedistal end of the elongated body. The ultrasonic transducer phased arrayis configured to emit and receive ultrasonic energy for volumetricscanning from the distal end of the elongated body.

The present invention also provides improved imaging over the prior artas applied to minimally invasive surgical procedures. In particular, areal time three dimensional ultrasonic imaging probe apparatusconfigured to be placed into a body, includes a cannula configured toprovide access to a cavity inside the body. An elongated body, havingproximal and distal ends, is configured to extend into the body via thecannula. An ultrasonic transducer phased array is connected to and ispositioned on the distal end of the elongated body. The ultrasonictransducer phased array is configured to emit ultrasonic energy forvolumetric scanning from the distal end of the elongated body andreceive reflected ultrasonic energy.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a real time three dimensional ultrasonicimaging system;

FIG. 2A is an enlarged partial perspective view an imaging probeconfigured to emit and receive ultrasonic energy for volumetric forwardscanning according to the present invention;

FIG. 2B is an enlarged side view of an imaging probe of FIG. 2A;

FIG. 2C is an enlarged partial perspective view an imaging probeconfigured to emit and receive ultrasonic energy for volumetric sidescanning according to the present invention;

FIG. 2D is an enlarged side view of an imaging probe of FIG. 2C;

FIG. 2E is an enlarged view of elements of an ultrasonic transducerphased array according to the present invention;

FIG. 2F is an enlarged view of elements of a sparsely populated periodicultrasonic transducer phased array with tools according to the presentinvention;

FIG. 2G is an enlarged view of a row of ultrasonic transducer elementsand a column of ultrasonic transducer elements with tools according tothe present invention;

FIG. 3A is an enlarged cross-sectional view of a real time threedimensional imaging probe apparatus configured to emit and receiveultrasonic energy for volumetric forward scanning according to thepresent invention;

FIG. 3B is an enlarged cross-sectional view of a real time threedimensional imaging probe apparatus configured to emit and receiveultrasonic energy for volumetric side scanning according to the presentinvention;

FIG. 4A is an enlarged cross-sectional view of an ultrasonic transducerphased array and electrode according to the present invention;

FIG. 4B is an enlarged view of a distal end of an ultrasonic transducerphased array and electrode partially overlying the ultrasonic transducerphased array according to the present invention;

FIG. 5A is a cross-sectional view of a real time three dimensionalimaging probe apparatus configured to emit and receive ultrasonic energyfor volumetric forward scanning according to the present invention;

FIG. 5B is a cross-sectional view of a real time three dimensionalimaging probe apparatus configured to emit and receive ultrasonic energyfor volumetric side scanning according to the present invention;

FIG. 6A is a cross-sectional view of a real time three dimensionalimaging biopsy apparatus configured to emit volumetric forward scanningultrasonic energy according to the present invention;

FIG. 6B is a cross-sectional view of a real time three dimensionalimaging biopsy apparatus configured to emit volumetric side scanningultrasonic energy according to the present invention;

FIG. 7A is an enlarged cross-sectional view of a real time threedimensional catheter apparatus configured to emit and receive ultrasonicenergy for volumetric forward scanning and electrodes according to thepresent invention;

FIG. 7B is an enlarged cross-sectional view of a real time threedimensional catheter apparatus configured to provide side scanning andelectrodes according to the present invention; and

FIGS. 7C and 7D illustrate the use of a real time three dimensionalimaging catheter and electrode apparatus of FIG. 7A.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which a preferred embodimentof the invention is shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

FIG. 1 is a block diagram of an ultrasonic imaging system that providesreal time three dimensional ultrasonic images. The imaging probe 110 isa real time three dimensional imaging catheter, biopsy probe, surgicalor endoluminal probe (such as arectal, prostate, transurethal, orintravaginal probe) that can be configured to provide either forward orside scanning volumetric scanning ultrasonic energy via an ultrasonictransducer phased array under the control of the controller/signalprocessor 105. The imaging probe 110 can be inserted into a region ofinterest (such as a inside the body of a patient) to provide real timethree dimensional ultrasonic imaging of objects within the region ofinterest. For example, the imaging probe 110 can be a real time threedimensional imaging catheter used to provide imaging during cardiac orprostate procedures. Accordingly, the imaging catheter probe 110 wouldhave a diameter in the range between about 3 French and 20 French.Alternately, the imaging probe 110 can provide imaging during needlebiopsy or minimally invasive surgical procedures (such as in conjunctionwith a trocar during knee or abdominal surgery). Accordingly, theimaging probe would have a diameter in the range between about 1millimeter (mm) and 20 mm. The imaging probe can include mechanical,surgical, and therapeutic tools (such as a suction tool, an opticalfiber, a guide wire, or a scalpel blade) and electrodes to monitor ortreat a particular tissue (such as electrophysiological or ablationelectrodes). As described herein, a configuration for the emission ofultrasonic energy for volumetric scanning includes a configuration forthe emission of volumetric forward scanning ultrasonic energy and aconfiguration for the emission of volumetric side scanning ultrasonicenergy.

The controller/signal processor 105 transmits/receives electrical pulsesto/from imaging probe 110. For example, the controller/signal processor105 transmits electrical pulses to the imaging probe 110 that cause theultrasonic transducer phased array to emit ultrasonic energy. Thecontroller/signal processor also receives electrical pulses from theimaging probe 110 caused by the incidence of ultrasonic energy reflectedfrom objects within the region of interest upon the ultrasonictransducer phased array. The controller/signal processor 105 provides avolumetric image on the display 100 of the object within the region ofinterest based on the electrical pulses received from the imaging probe110. For example, the image may be formed using the systems andtechniques disclosed in U.S. Pat. No. 5,546,807 to Oxaal et al. entitledHigh Speed Volumetric Ultrasound Imaging System. The display can be acathode ray tube, liquid crystal display, or other device with suitabledynamic range for the display of volumetric images.

FIGS. 2A and 2B are enlarged partial perspective and side views of animaging probe 110 configured to emit and receive ultrasonic energy forvolumetric forward scanning according to the present invention. Theimaging probe includes an elongated body 200 having proximal and distalends. The ultrasonic transducer phased array 205 is connected to andpositioned on the distal end of the elongated body 200, and positionedto emit and receive ultrasonic energy for volumetric forward scanningfrom the distal end of the elongated body 200. Imaging is provided byinserting the imaging probe into the region of interest (such as thebody of a patient) so that the ultrasonic energy emitted from theultrasonic transducer phased array is incident upon and is reflectedfrom an object within the region of interest (such as tissue). The termbody, as used herein, includes a biological entity, such as a humanbody, animal body, or vessel or container filled with fluid or airbornemedia subject to on-destructive evaluation (such as a nuclear reactorvessel).

The cable 210 provides a plurality of conductors (such as wires oroptical fibers) for transmission of signals to/from thecontroller/signal processor 105. In one embodiment, the cable 210includes 70 conductors.

FIGS. 2C and 2D are enlarged partial perspective and side views of animaging probe 110 configured to emit and receive ultrasonic energy forvolumetric side scanning according to the present invention. Sidescanning can provide a real time three dimensional image of objectslocated such that rotation of a forward scanning probe described aboveis less practical (such as a cardiac ventricular wall). The ultrasonictransducer phased array 206 is positioned substantially parallel to thelongitudinal axis 211 of the elongated body 200 to provide side scanningultrasonic energy. It should be understood that substantially parallelincludes an orientation of the ultrasonic transducer phased array thatis within +/-45 degrees of a completely parallel orientation.

FIG. 2E is an illustration of a preferred embodiment of an ultrasonictransducer phased array 205 connected to and positioned on the distalend of the elongated body 200 to emit volumetric forward or sidescanning ultrasonic energy wherein the ultrasonic transducer phasedarray 205 covers a major portion of the distal end of the elongated body200 (more than 50% of the distal end of the elongated body). Theultrasonic transducer phased array 205 is formed in an octagonal shapeso as to increase the number of ultrasonic transducer elements includedin the ultrasonic transducer phased array 205 positioned on the distalend of the elongated body. The ultrasonic transducer phased arrayoperates at about 5 megahertz (MHz), includes 70 elements spaced about0.2 mm apart, and is about 3 mm in diameter.

The ultrasonic transducer phased array 205 includes a plurality ofultrasonic transducer transmit and receive elements (elements) 215arranged in row and column configuration. The elements can be arrangedas a sparse array, a fully populated array (such as 10×10, 20×20, 60×60,80×80), a Mills Cross array, a random distribution array, or a periodicdistribution array. The ultrasonic transducer elements 215 receiveelectrical pulses from the controller/signal processor 105, as describedabove, causing the ultrasonic transducer elements 215 to emit ultrasonicenergy. Furthermore, the ultrasonic transducer elements are providedwith electrical pulses according to a phase sequence in the row andcolumn direction as described in U.S. Pat. No. 5,546,807 to Oxaal et al.to produce the volumetric image described therein. The emittedultrasonic energy is reflected from an object within the region ofinterest and is incident upon the elements 215 and thereby causing acorresponding electrical pulse to be transmitted to thecontroller/signal processor 105. The ultrasonic transducer phased arrayis made from a piezoelectric material.

The ultrasonic transducer phased array 205 is configured to cover amajority of the distal end of the elongated body 200 to provide a largeaperture relative to the prior art. In particular, an ultrasonictransducer phased array 205 may provide superior resolution, θ_(A)(resolution in the azimuth dimension) and θ_(A) (resolution in theelevation dimension), by increasing the azimuth and elevation dimensionsof the elongated body 200 allocated to the ultrasonic transducer phasedarray 205 according to: ##EQU1## where λ is the wavelength of theultrasonic energy and where L is the aperture size of the ultrasonictransducer phased array 205 in the elevation dimension and where D isthe aperture size of the ultrasonic transducer phase array in theazimuth dimension. A larger aperture size also provides increasedsensitivity (signal to noise ratio) in proportion to the improvedresolution described above. For example, in contrast to the ultrasonictransducer phased arrays described herein, the ultrasonic transducerphased arrays disclosed in Seward cover a minority of the elongated bodydescribed therein. Moreover, Seward discloses an ultrasonic transducerphased array in conjunction with conventional tools and electrodespositioned in close proximity to and outside of the ultrasonictransducer phased array, thereby limiting the size of the ultrasonictransducer phased array. As a result, the images produced by the priorart may have low spatial resolution and sensitivity relative to thoseproduced by the present invention. Moreover, the three dimensionalultrasound imaging of the prior art may be obscured when conventionaltools are used within the field of view of the ultrasonic transducerphased array

FIG. 2F is an enlarged view of elements of a sparsely populated periodicultrasonic transducer phased array with tools according to the presentinvention. The ultrasonic transducer phased array includes a pluralityof sites occupied by ultrasonic transducer elements 215. The ultrasonictransducer phased array 205 is divided into four quadrants: quadrant 1,quadrant 2, quadrant 3, and quadrant 4. At least one of the ultrasonictransducer elements is absent from the ultrasonic transducer phasedarray, thereby defining an interstitial site. A tool can be positionedat the interstitial site to provide therapy to or monitoring of tissue.In a preferred embodiment, a plurality of ultrasonic transducer elements215 are absent, thereby defining a plurality of interstitial siteshaving a circular arrangement 224 in which a plurality of tools can bepositioned.

The circular arrangement 224 allows tools 222, 226, 228, and 230 to bepositioned within the ultrasonic transducer phased array 205 andprovides improved image resolution and sensitivity and reduces theeffect of side lobes produced by smaller array dimensions as describedabove. The plurality of tools are distributed among the quadrants toreduce the side lobe effects caused by the presence of the tools. Forexample, tool 222 is positioned in quadrant 1, tool 226 is positioned inquadrant 2, tool 228 is positioned in quadrant 3, and tool 230 ispositioned in quadrant 4. The tools may be a fiber optic lead, anablation electrode, an electrophysiological electrode, a suction tool,or a guide wire. The inclusion of tools within the ultrasonic transducerphased array 205 allows the user to align the tool with the tissue moreaccurately, thereby making the imaging probe easier to use and moreeffective.

FIG. 2G is an enlarged view of a row of ultrasonic transducer elementsand a column of ultrasonic transducer elements (a Mills cross array)with tools according to the present invention. The combination of therow of ultrasonic transducer elements and the column of ultrasonictransducer elements define four quadrants of the ultrasonic transducerphased array: quadrant 1, quadrant 2, quadrant 3, and quadrant 4. Thequadrants include a plurality of interstitial sites 221 from whichultrasonic transducer elements 215 are absent.

The sparse array may be implemented by selectively connecting a sub-setof conductors included in the cable 210 to corresponding elements 215.For example, a sparse array may be implemented using a single row andcolumn of ultrasonic transducer elements in combination. The row andcolumn ultrasonic transducer elements are provided with electricalpulses and receive mode delays according to the phasing described above.Alternately, the elements 215 within the ultrasonic transducer phasedarray 205 may be arranged according to a periodic distribution in whichthe spacing between transmit and receive elements is different so as toreduce grating lobe and side lobe effects. Another alternativedistribution includes a random array geometry with a gaussian samplingof the transmit elements and a uniform sampling of the receive elements.

In one embodiment, tools 222, 226, 228, and 230 are positioned atinterstitial sites in the quadrants 1, 2, 3, and 4 defined by the rowand column of ultrasonic transducers. In a preferred embodiment, asingle tool is positioned in each quadrant so as to minimize the effectsof side lobes on the imaging. The tools may be a fiber optic lead, anablation electrode, an electrophysiological electrode, a suction tool,or a guide wire. The inclusion of tool within the ultrasonic transducerphased array allows the user to align the tool with the tissue moreaccurately, thereby making the imaging probe easier to use and moreeffective.

FIG. 3A is an enlarged cross-sectional view of a real time threedimensional imaging probe apparatus configured to emit volumetricforward scanning ultrasonic energy according to the present invention. Aplurality of conductors 300 within the cable 210, having proximal anddistal ends, are suitable for conducting electrical impulses to and fromthe corresponding elements 215 of the ultrasonic transducer phased array205. The plurality of conductors 300 pass through a plurality of spacedholes 315 in the mounting plate 305 having a first and second side. Theplurality of conductors 300 are connected to corresponding elements 215within the ultrasonic transducer phased array 205 that is connected toand overlying the second side of the mounting plate 305.

A backing material 335 is positioned between the mounting plate 305 andthe distal end of the elongated body 210. The acoustic impedance of thebacking material 335 is matched to the acoustic impedance of themounting plate 305 to reduce the amount of acoustic energy reflectedback to the ultrasonic transducer phased array 205. The mounting plate305 is made from a material which is acoustically transparent toultrasonic energy at the resonant frequency of the ultrasonic transducerphased array 205. The term acoustically transparent, in the frequencyband, includes materials that reflect a portion of an incidentultrasonic energy in the range between about 50% and 0% of the incidentultrasonic energy. For example, the mounting plate 305 can be a softpolymer material such as polyimide. In a preferred embodiment, theimpedance of the mounting plate 305 is in the range between about 2MRayls and 5 MRayls.

The plurality of holes 315 in the mounting plate 305 are spaced toaccommodate the spacing of the elements 215 within the ultrasonictransducer phased array 205. In a preferred embodiment, the hole spacing320 is about 0.2 mm on center and the hole diameter 325 is about 0.1 mm.In a preferred embodiment, the holes 315 are created using a CO₂ orexcimer laser. The CO₂ or excimer laser can avoid over-stressing themounting plate while the holes 315 are created and may be controlledwith greater precision than can mechanical drilling. In one embodiment,the holes 315 are filled with a conductive epoxy. The plurality ofconductors 300 are connected to the conductive epoxy. In anotherembodiment, the plurality of conductors 300 pass through the holes 315and are connected to the plurality of corresponding elements 215. Theholes 315 are then filled with the conductive epoxy.

In the prior art, mechanical drilling of holes with a diameter andspacing described above may over-stress the mounting plate material,thereby causing a failure of the mounting plate. Moreover, control andaccuracy of a mechanical drilling process may be difficult at thedimensions described above. Furthermore, a drill bit capable of drillinga hole having a diameter of about 0.1 mm may be difficult to obtain andmay be prone to failure.

The mounting plate 305 is formed to a thickness, D, that does not exceed

    D=λ

where λ is the wavelength of the ultrasonic energy emitted by theultrasonic transducer phased array. For example, for ultrasonic energyemitted at 5 MHz, the thickness of the mounting plate 305 should notexceed 0.075 mm. The thickness described above may provide additionalstructural integrity to the mounting plate 305. Consequently, themounting plate 305 may be better suited to the creation of the holes 315having the hole diameter 325 and the hole spacing 320 described above.

FIG. 3B is an enlarged cross-sectional view of a real time threedimensional imaging probe apparatus configured to emit volumetric sidescanning ultrasonic energy according to the present invention. A conduit330 having proximal and distal ends includes a plurality of conductors337 having proximal and distal ends. The distal end of the conduit 330is positioned substantially parallel to the ultrasonic transducer phasedarray 205 to allow a plurality of pads 339, positioned at the distal endof the plurality of conductors 337, to be directly connected to aplurality of corresponding elements of the ultrasonic transducer phasedarray 205. A backing material 335 is positioned between the conduit 330and the distal end of the elongated body 210. The backing material 335is acoustically matched to the mounting plate 305 to reduce thereflection of acoustic energy emitted from the ultrasonic transducerphased array 205. A glue is positioned between the conduit 300 and theultrasonic transducer phased array 205 to maintain the position of theconduit 300 with respect to the ultrasonic transducer phased array 205.It will be understood that the phrase directly connect, as used herein,includes in contact with and having layers positioned between themounting plate 305 and the conduit 330.

The conduit 330 can be a Multilayer Flexible Circuit (MFC) that includesthe conductors 337 and the pads 339. The conductors 337 can be on theouter surface and the interior of the MFC. The MFC can be orientedwithin the elongated body to provide a direct connection to the mountingsheet 305. The pads 339 of the MFC are aligned with the elements of theultrasonic transducer phased array.

FIG. 4A is an enlarged cross-sectional view of an ultrasonic transducerphased array 205 and electrode assembly 400 according to the presentinvention. The ultrasonic transducer phased array 205 is connected toand positioned on the distal end of the elongated body 200 andpositioned to emit and receive ultrasonic energy for volumetric forwardscanning of objects within the region of interest. The electrodeassembly 400 is connected to and overlying the ultrasonic transducerphased array 205. The electrode assembly 400 includes a first groundlayer 405 connected to and overlying the ultrasonic transducer phasedarray 205. The first ground layer 405 can be implemented with a metallayer having a thickness in the range between about 0.02 μm and 20 μm.The first ground layer 405 is formed by sputter deposition, plating, abonded foil, a screen print, or vapor deposition. The first insulatorlayer 410 is connected to and overlying the first ground layer 405. Thefirst insulator layer 410 is formed from polymide to a thickness in therange between about 0.02 μm and 20 μm. The second ground layer 415 isconnected to and overlying the first insulator layer 410 and can beimplemented with a metal layer having a thickness in the range betweenabout 0.02 μm and 20 μm. The second insulator layer 420 is connected toand overlying the second ground layer 415 and can be implemented usingpolymide formed to a thickness in the range between about 0.02 μm and 20μm. The electrode 425 is connected to and overlying the second insulatorlayer 420.

As described above, the electrode assembly is transparent to ultrasonicenergy. Consequently, the thickness, D, of the electrode assembly 400does not exceed:

    D=λ

where λ is the wavelength of the ultrasound energy emitted by theultrasonic transducer phased array. For example, for ultrasonic energyof 5 MHz, the thickness, D, of the electrode assembly 400 is less thanabout 0.075 mm.

It should be understood that the phrase connected to, as used herein,includes an arrangement wherein the a first component is physicallycontacting a second component and an arrangement wherein at least athird component is positioned between the first and second components.Accordingly, the above description includes an arrangement wherein othercomponents are positioned between the ultrasonic transducer phased array205 and the electrode 425.

The electrode 425 can be used to perform therapy on or monitoring oftissue within the region of interest. For example, the electrode 405 maybe an electrocardiogram electrode or electrophysiological mappingelectrode used to monitor the activity of heart tissue. Alternately, theelectrode 425 can be an ablation electrode used to deliver a stimulus tothe tissue within the region of interest. For example, the electrode maybe used to deliver a radiofrequency thermal ablation in the rangebetween about 5 Watts to 30 Watts at a frequency in the range betweenabout 300 Hz to 750 kHz.

The position of the electrode 425 connected to and overlying theultrasonic transducer phased array 205 may provide, in combination withthe ultrasonic transparency of the electrode assembly, improved guidanceof the electrode to the targeted tissue within the region of interest.The electrode 425 can be positioned by aligning the image with thetissue, thereby possibly reducing complications associated with thealignment of the electrode 425 and the image presented to the user inthe prior art. The function of the electrode 425 may be controlled bythe controller/signal processor 105 via a guide wire 440 extendingthrough the elongated body 200, through the ultrasonic transducer phasedarray 205, and through the electrode assembly 400. Alternately, theelectrode 425 may be controlled via a wire 435 that is connected to theelectrode 425 without passing through the electrode assembly 400. Inanother embodiment, a fiber optic lead 450 extends through theultrasonic transducer phased array and the electrode assembly 400. Laserlight is emitted from the fiber optic lead to provide therapy to aparticular tissue.

FIG. 4B is an enlarged view of the distal end of an ultrasonictransducer phased array and electrode partially overlying the ultrasonictransducer phased array and tools according to the present invention.The electrode 425 described above, can be used in combination with thetools described herein. The electrode 425 is connected to and overlyingthe ultrasonic transducer phased array 205. The ultrasonic transducerphased array 205 includes a plurality of sites occupied by ultrasonictransducer elements 215. At least one of the ultrasonic transducerelements 215 is absent from a site, defining an interstitial site 480. Atool 455 is positioned at the interstitial site 480. The electrode 425does not overlie the tool 455 positioned at the interstitial site 480.The electrode 425, thereby, may not interfere with the operation of thetool. In another embodiment, a plurality of tools 455, 460, 465, and 470are positioned at a plurality of interstitial sites.

FIG. 5A is a cross-sectional view of a real time three dimensionalimaging probe apparatus configured to emit and receive ultrasonic energyfor volumetric forward scanning according to the present invention. Theapparatus shown in FIG. 5A may be used for minimally invasive surgicalprocedures such as laparoscopic surgery. Laparoscopic surgery mayinvolve the insertion of the cannula 500 through an incision to provideaccess to a cavity within the body. The cannula 500 provides a surgicalport through which tools may access the cavity. The distal end of theelongated body 505 extends through the cannula 500 into the cavity. Theultrasonic transducer phased array 205 is connected to the distal end ofthe elongated body 505 and is configured to emit volumetric forwardscanning ultrasonic energy from the distal end of the elongated body 505and receive reflected ultrasonic energy.

The present invention provides a three dimensional ultrasonic image ofthe region of interest to the user, thereby possibly allowing lesscomplicated manipulation of the imaging probe in relation to the tissue.In contrast, the prior art may include a B-mode or slice scanner forsurgical procedures of the type described above. The user may thereforeneed to mentally re-orient the B-mode image to aid in locating andapplying the imaging probe.

In one embodiment, tools are combined with the volumetric forwardscanning imaging probe as described herein. The ultrasonic transducerphased array 205 includes a plurality sites occupied by a plurality ofultrasonic transducer elements. At least one of the ultrasonictransducer elements is absent from a site, thereby defining aninterstitial site. A tool is positioned at the interstitial site.

FIG. 5B is a cross-sectional view of a real time three dimensionalimaging probe apparatus configured to provide side scanning ultrasonicenergy according to the present invention. Side scanning can provide areal time three dimensional image of objects located such that rotationof a forward scanning probe described above is less practical (such as acardiac ventricular wall). The ultrasonic transducer phased array 205 ispositioned substantially parallel to a longitudinal axis of theelongated body 400 and configured to emit volumetric side scanningultrasonic energy and receive reflected ultrasonic energy.

In one embodiment, tools are combined with the volumetric side scanningimaging probe described above. The ultrasonic transducer phased array206 includes a plurality sites occupied by a plurality of ultrasonictransducer elements. At least one of the ultrasonic transducer elementsis absent from a site, thereby defining an interstitial site. A tool ispositioned at the interstitial site.

FIG. 6A is a cross-sectional view of a real time three dimensionalimaging biopsy apparatus configured to emit volumetric forward scanningultrasonic energy according to the present invention. The apparatusshown in FIG. 6A may be used for biopsy procedures wherein the biopsyneedle 600, having a proximal and distal end, is pointed at the distalend and is configured for insertion into a body. For example, the biopsyneedle may have a core element that is removed after insertion into thebody. After the core element is removed, the distal end of the elongatedbody 610 is inserted into the hollow core of the biopsy needle 600 andextended into the body. The ultrasonic transducer phased array 205 isconnected to and overlies the distal end of the elongated body 610 andis configured to emit volumetric forward scanning ultrasonic energy.

In one embodiment, tools are combined with the volumetric forwardscanning imaging biopsy apparatus as described herein. The ultrasonictransducer phased array 205 includes a plurality sites occupied by aplurality of ultrasonic transducer elements. At least one of theultrasonic transducer elements is absent from a site, thereby definingan interstitial site.

The present invention provides an ultrasonic transducer phased array 205to provide the user with images of the region of interest, therebyallowing less complicated manipulation of the biopsy apparatus inrelation to the tissue. In contrast, the prior art my include a B-modeor slice scanner for surgical procedures of the type described above.The user, therefore, may need to mentally re-orient the B-mode image toperform the biopsy.

FIG. 6B is a cross-sectional view of a real time three dimensionalimaging biopsy apparatus configured to provide volumetric side scanningultrasonic energy according to the present invention. After the coreelement is removed, the distal end of the elongated body 610 is insertedinto the hollow core of the biopsy needle 606 and extended into thebody. The ultrasonic transducer phased array 205 is positionedsubstantially parallel to a longitudinal axis of the elongated body 610to emit volumetric side scanning ultrasonic energy.

In one embodiment, tools are combined with the volumetric side scanningimaging biopsy apparatus described herein. The ultrasonic transducerphased array 205 includes a plurality sites occupied by a plurality ofultrasonic transducer elements. At least one of the ultrasonictransducer elements is absent from a site, thereby defining aninterstitial site. A tool is positioned at the interstitial site. Sidescanning can provide a real time three dimensional image of objectslocated such that rotation of a forward scanning probe described aboveis less practical (such as a breast tumor).

The imaging probes for biopsy and minimally invasive surgical proceduresdescribed herein can exist as unit wherein the components are connected.Alternately, the components may be available as a kit wherein thecomponents are assembled for use. For example, the components can beavailable as a sterile kit that includes each of the components.

FIG. 7A is an enlarged cross-sectional view of a real time threedimensional imaging catheter apparatus configured to emit volumetricforward scanning ultrasonic energy and an electrode according to thepresent invention. The catheter shown in FIG. 7A can be used for cardiacdiagnosis and treatment by positioning the elongated body 200, havingproximal and distal ends, using the three dimensional imaging providedby the ultrasonic transducer phased array 205 that is connected to andoverlies the distal end of the elongated body 200. The ultrasonictransducer phased array 205 is positioned to emit volumetric forwardscanning ultrasonic energy from the distal end of the elongated body200. A plurality of electrodes 700 and 701 are connected to andpositioned around a perimeter of the elongated body 200 substantiallyperpendicular to a longitudinal axis of the elongated body 200.Electrodes 700 and 701 can be electrophysiological mapping electrodesused to monitor the tissue in contact with the electrodes 700 and 701.In a preferred embodiment, the electrodes 700 and 701 are positionedaround the perimeter of the elongated body 200 so as to provide contactwith the tissue regardless of the rotation of the elongated body 200.The electrodes 700 and 701 may also be ablation electrodes that providetherapy to the contacted tissue as described herein.

FIG. 7B is an enlarged cross-sectional view of a real time threedimensional imaging catheter apparatus configured to provide sidescanning and an electrode according to the present invention. Sidescanning can provide a real time three dimensional image of objectslocated such that rotation of a forward scanning catheter describedabove is less practical (such as a cardiac ventricular wall). Theapparatus shown in FIG. 7B may be used to locate tissue and apply theelectrodes 700 and 701 in areas where the rotation of the imagingcatheter of FIG. 7A is impractical.

In FIG. 7C, the real time three dimensional imaging catheter apparatusis used locate tissue within the region of interest. In FIG. 7D, thereal time three dimensional imaging catheter apparatus is used tomonitor the tissue as described above. For example, the volumetricforward scanning ultrasonic catheter may be used to image theendocardium. When the desired tissue is located, the catheter ispositioned parallel to the endocardium and the plurality of electrodesare used to treat the located tissue.

The present invention provides volumetric scanning ultrasonic imagingprobes and catheters in combination with tools to provide therapy totissue of interest. In particular, the tool can be a fiber optic lead, asuction tool, a guide wire, an electrophysiological electrode, or anablation electrode. Positioning the tool at an interstitial site allowsa large ultrasonic transducer phased array aperture, thereby producingsuperior image resolution and sensitivity as compared to the prior art.Positioning the tool within the ultrasonic transducer phased arrayallows the user to align the tool with the tissue to be treated moreaccurately, thereby making the probe easier to use and more effective.Conventional probes may include tools, positioned outside the ultrasonictransducer phased array, reducing the aperture size of the ultrasonictransducer phased array. A reduced aperture size provides lower imageresolution and sensitivity.

The present invention also provides increased image resolution byincreasing the aperture size of the ultrasonic transducer phased arrayto include a majority of the surface area of the distal end of elongatedbody. In particular, in contrast to the ultrasonic transducer phasedarrays described herein, the ultrasonic transducer phased arraysdisclosed in Seward cover a minority of the elongated body describedtherein. Moreover, Seward discloses an ultrasonic transducer phasedarray in conjunction with conventional tools and electrodes positionedin close proximity to the ultrasonic transducer phased array, therebylimiting the size of the ultrasonic transducer phased array. As aresult, the images produced by the prior art may have low spatialresolution and sensitivity relative to those produced by the presentinvention.

The present invention also provides improved imaging over the prior artas applied to biopsy and minimally invasive surgical procedures. Inparticular, the present invention provides a three dimensionalultrasonic image of the region of interest to the user, thereby possiblyallowing less complicated manipulation of the electrode assembly inrelation to the tissue. In contrast, the prior art may include a B-modeor slice scanner for surgical procedures of the type described above.The user may therefore need to mentally re-orient the B-mode image toaid in locating and applying the electrode assembly.

The present invention also provides real time three dimensional imagingprobes with ultrasonically transparent electrodes for use withcatheters. The ultrasonically transparent electrode may enable the userto more easily apply the electrode to tissue within a region ofinterest, thereby allowing a reduction in the complexity associated withthe prior art. For example, the present invention may enable the user toapply the electrode to the tissue by locating the tissue within theregion of interest using the real time three dimensional images. Incontrast, users of imaging probes in the prior art may locate the tissueand then manipulate a tool to the tissue by understanding theregistration between the image and the physical location of theelectrode on the probe. Moreover, the ultrasonically transparentelectrode may reduce the occlusion of the tissue.

In the drawings and specification, there have been disclosed typicalpreferred embodiments of the invention and, although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the invention being set forthin the following claims.

What is claimed is:
 1. A real time three dimensional ultrasound imagingprobe apparatus configured to be placed inside a body, the apparatuscomprising:an elongated body having proximal and distal ends; anultrasonic transducer phased array connected to and positioned on thedistal end of the elongated body, wherein the ultrasonic transducerphased array is configured to emit ultrasonic energy for volumetricscanning from the distal end of the elongated body and receive reflectedultrasonic energy, and wherein the ultrasonic transducer phased arraycomprises a plurality of sites occupied by ultrasonic transducerelements, wherein at least one ultrasonic transducer element is absentfrom at least one of the sites to define an off-center interstitial sitein the ultrasonic transducer phased array; and a tool, that extends fromthe proximal end of said elongated body to said off-center interstitialsite.
 2. The apparatus of claim 1, wherein the tool comprises a guidewire, a suction tool, a scalpel, an ablation electrode, a fiber opticlead, or an electrophysiological mapping electrode.
 3. The apparatus ofclaim 1, wherein a plurality of ultrasonic transducer elements areabsent from a plurality of sites to define a plurality of interstitialsites, wherein the plurality of interstitial sites have a circulararrangement within the ultrasonic transducer phased array.
 4. Theapparatus of claim 1, wherein the plurality of ultrasonic transducerelements are arranged in a row of ultrasonic transducer elements and acolumn of ultrasonic transducer elements, wherein the row of ultrasonictransducer elements is substantially perpendicular to the column ofultrasonic transducer elements; and wherein the row of ultrasonictransducer elements and the column of ultrasonic transducer elementsdefine four quadrants of interstitial sites within the ultrasonictransducer phased array.
 5. The apparatus of claim 4, further comprisinga plurality of tools, wherein at least one of the plurality of tools ispositioned at an interstitial site within each quadrant of theultrasonic transducer phased array.
 6. The apparatus of claim 1, whereinthe ultrasonic transducer phased array is positioned on the distal endof the elongated body substantially parallel to a longitudinal axis ofthe elongated body to emit and receive ultrasonic energy for volumetricside scanning.
 7. The apparatus of claim 1, further comprising aplurality of electrodes connected to and positioned around a perimeterof the elongated body substantially perpendicular to a longitudinal axisof the elongated body.
 8. The apparatus of claim 1, wherein theultrasonic transducer phased array covers a major portion of the distalend of the elongated body.
 9. The apparatus of claim 1, furthercomprising an electrode assembly connected to and overlying theultrasonic transducer phased array, wherein the electrode assembly istransparent to ultrasonic energy wherein the electrode assemblycomprises:a first ground layer connected to and overlying the ultrasonictransducer phased array having a thickness in a range between about 0.02μm and 20 μm; a first insulator layer connected to and overlying thefirst ground layer having a thickness in the range between about 0.02 μmand 20 μm; and an electrode connected to and overlying the firstinsulator layer.
 10. The apparatus of claim 9, wherein the electrodeassembly includes an electrode comprising an ablation electrode or anelectrophysiological mapping electrode.
 11. The apparatus of claim 9,wherein the electrode assembly has a thickness that does not exceedabout a wavelength of the ultrasonic energy emitted by the ultrasonictransducer phased array.
 12. The apparatus of claim 9, wherein theelectrode assembly comprises:a first ground layer connected to andoverlying the ultrasonic transducer phased array having a thickness in arange between about 0.02 μm and 20 μm; a first insulator layer connectedto and overlying the first ground layer having a thickness in the rangebetween about 0.02 μm and 20 μm; a second ground layer connected to andoverlying the first insulator having a thickness in the range betweenabout 0.02 μm and 20 μm; a second insulator layer connected to andoverlying the second ground layer having a thickness in the rangebetween about 0.02 μm and 20 μm; and an electrode connected to andoverlying the second insulator layer.
 13. A real time three dimensionalultrasound imaging probe apparatus configured to be placed inside abody, the apparatus comprising:an elongated body having proximal anddistal ends; an ultrasonic transducer phased array connected to andpositioned on the distal end of the elongated body, wherein theultrasonic transducer phased array is configured to emit ultrasonicenergy for volumetric scanning from the distal end of the elongated bodyand receive reflected ultrasonic energy; and an electrode assembly,connected to and overlying the ultrasonic transducer phased array,wherein the electrode assembly is transparent to ultrasonic energy,wherein the electrode assembly comprises:a first ground layer connectedto and overlying the ultrasonic transducer phased array having athickness in a range between about 0.02 μm and 20 μm, a first insulatorlayer connected to and overlying the first ground layer having athickness in the range between about 0.02 μm and 20 μm; and an electrodeconnected to and overlying the first insulator.
 14. The apparatus ofclaim 13, wherein the ultrasonic transducer phased array comprises aplurality of sites occupied by ultrasonic transducer elements, whereinat least one ultrasonic transducer element is absent from at least onesite to define an interstitial site in the ultrasonic transducer phasedarray, wherein said electrode assembly is absent from a position on thedistal end of the elongated body that corresponds to the interstitialsite; and wherein the apparatus further comprises a tool, that extendsfrom the proximal end of said elongated body to said interstitial site.15. The apparatus of claim 14, wherein a plurality of elements areabsent from a plurality of sites to define a plurality of interstitialsites, and wherein the plurality of interstitial sites have a circulararrangement within the ultrasonic transducer phased array.
 16. Theapparatus of claim 13, wherein the ultrasonic transducer phased arraycovers a major portion of the distal end of the elongated body.
 17. Theapparatus of claim 13, wherein the electrode assembly includes anelectrode comprising an ablation electrode or an electrophysiologicalmapping electrode.
 18. The apparatus of claim 13, wherein the ultrasonictransducer phased array is positioned substantially parallel to alongitudinal axis of the elongated body to emit volumetric side scanningultrasonic energy and receive reflected ultrasonic energy.
 19. Theapparatus of claim 13, further comprising a plurality of electrodesconnected to and positioned around a perimeter of the elongated bodysubstantially perpendicular to a longitudinal axis of the elongatedbody.
 20. The apparatus of claim 13, wherein the electrode assembly hasa thickness that does not exceed about a wavelength of the ultrasonicenergy emitted by the ultrasonic transducer phased array.
 21. Theapparatus of claim 13, wherein the electrode assembly comprises:a firstground layer connected to and overlying the ultrasonic transducer phasedarray having a thickness in a range between about 0.02 μm and 20 μm; afirst insulator layer connected to and overlying the first ground layerhaving a thickness in the range between about 0.02 μm and 20 μm; asecond ground layer connected to and overlying the first insulatorhaving a thickness in the range between about 0.02 μm and 20 μm; asecond insulator layer connected to and overlying the second groundlayer having a thickness in the range between about 0.02 μm and 20 μm;and an electrode connected to and overlying the second insulator. 22.The apparatus of claim 13, wherein the ultrasonic transducer phasedarray comprises a plurality of sites occupied by ultrasonic transducerelements, wherein at least one ultrasonic transducer element is absentfrom at least one site to define an interstitial site in the ultrasonictransducer phased array, the apparatus further comprising a fiber opticlead that extends from the proximal end of said elongated body to saidinterstitial site.
 23. A real time three dimensional imaging biopsyapparatus configured to be inserted into a body, the apparatuscomprising:a biopsy needle, configured to be inserted into the body; anelongated body having proximal and distal ends, wherein the distal endis configured to be extended into the biopsy needle; an ultrasonictransducer phased array connected to and positioned on the distal end ofthe elongated body, wherein the ultrasonic transducer phased array isconfigured to emit forward scanning ultrasonic energy for volumetricscanning from the distal end of the elongated body and receive reflectedultrasonic energy.
 24. The apparatus of claim 23, wherein the ultrasonictransducer phased array comprises a plurality of sites occupied byultrasonic transducer elements, wherein at least one ultrasonictransducer element is absent from at least one of the sites to define aninterstitial site in the ultrasonic transducer phased array; and whereinthe apparatus further comprises a tool that extends from the proximalend of said elongated body to said interstitial site.
 25. The apparatusof claim 24, wherein the tool comprises a suction tool or a cuttingtool.
 26. A real time three dimensional ultrasonic imaging probeapparatus configured to be placed into a body, the apparatuscomprising:a cannula configured to provide access to a cavity inside thebody; an elongated body having proximal and distal ends, wherein thedistal end is configured to be extended through the cannula; anultrasonic transducer phased array connected to and positioned on thedistal end of the elongated body, wherein ultrasonic transducer phasedarray is configured to emit ultrasonic energy for volumetric scanningfrom the distal end of the elongated body and receive reflectedultrasonic energy, wherein the ultrasonic transducer phased arraycomprises a plurality of sites occupied by ultrasonic transducerelements, wherein at least one ultrasonic transducer element is absentfrom at least one of the sites to define an interstitial site in theultrasonic transducer phased array; and wherein the apparatus furthercomprises a tool that extends from the proximal end of said elongatedbody to said interstitial site.
 27. The apparatus of claim 26, whereinthe ultrasonic transducer phased array is positioned substantiallyparallel to a longitudinal axis of the elongated body to emit volumetricside scanning ultrasonic energy and receive reflected ultrasonic energy.28. A real time three dimensional imaging catheter apparatus configuredto emit ultrasonic energy and receive reflected ultrasonic energy, theapparatus comprising:an elongated body having proximal and distal ends;an ultrasonic transducer phased array connected to and positioned on thedistal end of the elongated body wherein the ultrasonic transducerphased array is configured to emit ultrasonic energy for volumetricscanning from the distal end of the elongated body and receive reflectedultrasonic energy; and a plurality of electrodes connected to andpositioned around a perimeter of the elongated body substantiallyperpendicular to a longitudinal axis of the elongated body.
 29. Theapparatus of claim 28, wherein the ultrasonic transducer phased array ispositioned substantially parallel to a longitudinal axis of theelongated body to emit volumetric side scanning ultrasonic energy andreceive reflected ultrasonic energy.
 30. The apparatus of claim 28,wherein the ultrasonic transducer phased array comprises a plurality ofsites occupied by ultrasonic transducer elements, wherein at least oneultrasonic transducer element is absent from at least one of the sitesto define an interstitial site in the ultrasonic transducer phasedarray; and the apparatus further comprising a tool, that extends fromthe proximal end of said elongated body to said interstitial site. 31.The apparatus of claim 30, wherein the tool comprises a guide wire, asuction tool, an ablation electrode, a fiber optic lead, or anelectrophysiological mapping electrode.
 32. The apparatus of claim 30,wherein a plurality of elements are absent from a plurality of sites todefine a plurality of interstitial sites, wherein the plurality ofinterstitial sites have a circular arrangement within the ultrasonictransducer phased array.
 33. The apparatus of claim 29, furthercomprising an electrode assembly connected to and overlying the threedimensional ultrasonic transducer phased array, wherein the electrodeassembly is transparent to ultrasonic energy.
 34. A real time threedimensional ultrasonic imaging system comprising:a catheter having anelongated body with proximal and distal ends; an ultrasonic transducerphased array connected to and positioned on the distal end of theelongated body, wherein the ultrasonic transducer phased array isconfigured to emit ultrasonic energy for volumetric scanning from thedistal end of the elongated body and receive reflected ultrasonicenergy, and wherein the ultrasonic transducer phased array comprises aplurality of sites occupied by ultrasonic transducer elements; andwherein at least one ultrasonic transducer element is absent from atleast one of the sites to define an interstitial site in the ultrasonictransducer phased array; a tool that extends from the proximal end ofsaid elongated body to said interstitial site; a processor, responsiveto the catheter, that controls the emission of ultrasonic energy forvolumetric scanning from the ultrasonic transducer phased array andreceives reflected ultrasonic energy, wherein the processor producesimage data based on the received reflected ultrasonic energy; and adisplay, responsive to the processor, that produces an image based onthe image data produced by the processor.
 35. The system of claim 34,wherein the tool comprises a guide wire, a suction tool, an ablationelectrode, a fiber optic lead, or an electrophysiological mappingelectrode.
 36. The system of claim 34, wherein a plurality of elementsare absent from a plurality of sites to define a plurality ofinterstitial sites, wherein the plurality of interstitial sites have acircular arrangement within the ultrasonic transducer phased array. 37.The system of claim 34, further comprising an electrode assembly,connected to and overlying the distal end of the elongated body, whereinthe electrode assembly is transparent to ultrasonic energy.
 38. Thesystem of claim 34, wherein the ultrasonic transducer phased array ispositioned substantially parallel to a longitudinal axis of theelongated body to emit volumetric side scanning ultrasonic energy andreceive reflected ultrasonic energy.
 39. The system of claim 34, whereina plurality of electrodes are connected to and positioned around aperimeter of the elongated body substantially perpendicular to alongitudinal axis of the elongated body.
 40. The real time threedimensional ultrasound imaging probe apparatus of claim 1, wherein theelongated body comprises a catheter and the wherein the tool comprises aneedle configured to introduce a drug into the body.